The present invention relates to a positioning machine of original films for plate making on a base sheet, by which a print including a plurality of pages is obtained in a single operation.
As is well-known, color printing is performed by superimposing different colored inks by employing a plurality of printing plates which are produced by separating an original picture into several colors, such as cyan, magenta, yellow and black.
When a printing layout includes several pictures, each picture is generally color-separated independently and color separation films of each picture are made separately. Then, the color separation films for each color are collated and mounted on a transparent base and are printed in contact with a printing plate material to obtain an original color separation plate for printing of the desired layout.
It is essential that the various color plates print precisely in coincidence, to prevent "color mackle", which would otherwise impair the printing quality, and thus critical that the relative positions of the various pictures, mounted on the layouts for each color, exactly correspond.
Heretofore, several methods have been developed for performing the positioning operation of mounting the color separation films on the layouts. For example, in a conventional method the color separation films for each color are positioned in the desired layout by using register marks attached to a certain position of each color separation film by eye, and in another conventional method the positioning of the color separation films is performed by using a particular film positioning device, as disclosed in Japanese Patent Laying-Open Specification No. 53-93901 (Japanese Patent Application No. 52-7531).
In the latter case, the film positioning device comprises a rotary frame having a right regular polygonal prism shape, which is composed of a plurality of rectangular panels and is intermittently rotated around its axis so that each panel may be positioned in a predetermined position, and a pin-bar including register pins facing downward, which is adapted to be moved over the surface of the panel. A base sheet is mounted to each panel of the rotary frame, and original films of colors separated are consecutively mounted onto the base sheets at the corresponding positions on the panels by using the pin-bar.
This device is a very effective. However, since the rotary frame comprises the rectangular panels assembled in the right regular polygonal prism shape and is rotated, the size of the panels is restricted to be relatively small. Hence, it is not proper for positioning the original films on a large base sheet for a print including a plurality of pages. In FIG. 1 is shown a print or a book composition S including a plurality of pages, for example, eight pages in its one side. It is obtained by printing the eight pages portion in its one side in one operation and then the eight pages portion in the other side in another operation, and thus the obtained print S is folded up three times, thereby obtaining a section or signature of 16 pages.
When the size of one page is an A4 size (210.times.297 mm), the print S of FIG. 1 has an A1 size (594.times.841 mm). Therefore, in order to cover the A1 size sufficiently, the panel for mounting the base sheet should be designed to be somewhat larger than the A1 size, and accordingly the positioning device of the type described above will be made in large size. This requires the high cost of facilities, and further the height of working operation is raised, which is inconvenient for the daily work and reduces the productivity accordingly.
Consequently, the device of this kind is preferably made to a relatively small size type, and hence the color separation picture films are positioned in each page. For example, as shown in FIG. 2, on a base sheet 1 for covering one page, color separation picture films 2 and 3 are mounted in the desired layout positions by adhesive tapes 4, and the base sheet 1 is provided with register pin holes 5 adapting to register pins. The base sheet 1 on which the color separation picture films 2 and 3 are mounted, as shown in FIG. 2, will hereinafter be referred to as "an original film P".